AP_Scripting: add button example script

libraries/AP_Scripting/examples/button_test.lua.lua

@@ -0,0 +1,26 @@
+-- This script is an example button functionality
+
+local button_number = 1 -- the button numbber we want to read, as deffined in AP_Button
+
+local button_active_state = true -- the 'pressed' state of the button
+
+local last_button_state
+
+function update() -- this is the loop which periodically runs
+
+  local button_new_state = button:get_button_state(button_number) == button_active_state
+
+  -- the button has changes since the last loop
+  if button_new_state ~= last_button_state then
+    last_button_state = button_new_state
+    if button_new_state then
+      gcs:send_text(0, "LUA: Button pressed")
+    else
+      gcs:send_text(0, "LUA: Button released")
+    end
+  end
+
+  return update, 1000 -- reschedules the loop (1hz)
+end
+
+return update() -- run immediately before starting to reschedule